Core orientation

ABSTRACT

Core orientator for a core drill includes a face orientator and a bottom orientator supported by a shaft which extends into a shroud. A tubular extension is coupled to the shroud and is slidably coupled to a main body. The main body includes first and second latches. The first latches releasably lock the device to a core lifter case assembly disposed within the core drill, to selectively prevent the device from advancing in an uphole direction within the core drill. The latching system operates to prevent the device from falling out of the core drill. Face orientator includes a plurality of pins which can move axially to provide a plurality of profile reference points to a facing surface of a hole to be drilled. The bottom orientator includes a plurality of balls disposed within respective braces.

FIELD OF THE INVENTION

The present invention relates to an orientating device for providing anindication of the orientation of a ground core sample cut by a coredrill.

BACKGROUND OF THE INVENTION

Core sampling is typically employed to allow geological surveying of theground for purposes of exploration and/or mine development. Analysis ofthe material within the core sample provides information of thecomposition of the ground. However in order to map, for example a veinof ore, it is necessary to also have knowledge of the orientation of thecore sample relative to the ground from which it was cut.

Several systems are already known for orientating core samples. One suchsystem is the BALLMARK (Trademark) system which is described inInternational Application No. WO 00/75480. This system utilises a softmetal disk and a free running metal ball which are incorporated into aconventional inner tube back end or head assembly. The system utilisesthe force generated during breaking a core from the parent rock stratato indent the soft metal disk with the metal ball. As the ball is freerunning, gravity causes it to be positioned at the lowest point in itstrack, which corresponds with the bottom side of the hole andconsequently the bottom of the core.

The BALLMARK system has achieved high market acceptance and providesrelatively high core orientation accuracy. Nevertheless, one drawback ofthe BALLMARK system is that it only operates by the actual breaking ofthe core. Core breaking involves lifting a drill string into which thecore has advanced and applying sufficient tensile force to break thecore from the bottom of the hole being drilled by the drill. However, inhighly fractured or broken ground, the core breaks by itself during thedrilling process. In this instance, the BALLMARK system will notoperate.

A more rudimentary system for core marking involves running a markingtool, which in essence is in the form of a red pencil on the end of acounter balanced spear, by a wireline down the drill string tophysically mark the core. A substantial drawback with this system isthat it requires separate tripping of the tool down the hole which takessubstantial time thereby reducing actual drilling time and substantiallyincreasing the cost of coring.

Another marking system is the VAN RUTH wireline core orientator whichutilises a plurality of slidable pins to provide a contour of the faceof the core. Yet another system described in U.S. Pat. No. 4,311,201relies on the use of a malleable material to provide an imprint of theface of the core. However, again both these systems require the separatetripping of a tool in order to provide orientation of the core.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an orientationdevice for a core sample which does not require core breaking foroperation and can be incorporated into a standard core drill so that itdoes not require separate tripping.

According to the present invention there is provided an orientationdevice for providing an indication of the orientation of a core sampleof material relative to a body of material from which the core is cut,said orientation device including at least:

-   -   a main body provided with a latching system for releasably        latching the orientation device to a core lifter case assembly        coupled to a core tube of a core drill used to cut said core        sample; and,    -   a core orientation indicating means slidably coupled to said        main body for providing an orientation reference for said core        sample by action of contacting a facing surface of said material        to be drilled by said core drill prior to commencement of        drilling, said core orientation indicating means operatively        associated with said latching system whereby upon sliding of        said core orientation indicating means toward said main body        beyond a trigger point facilitated by advancing of said core        drill onto said facing surface said core orientation indicating        means disengages said latching system from said core lifter case        assembly so that said orientation device is retracted into said        core tube by an advancing core when said drill is operated to        cut said core.

Preferably said latching system includes first latching means forengaging said core lifter case assembly to prevent said main body frommoving in an uphole direction prior to core orientation indicating meansreaching said trigger point.

Preferably said latching system includes second latching means forengaging said core tube to prevent motion of said main body in adownhole direction.

Preferably said second latching means includes a brake mechanismsupported by said main body and having a plurality of brake elementswhich, when said main body is moved in a downhole direction relative tosaid core tube, wedge between said main body and an inner surface ofsaid core tube with increasing force to brake said relative motion andeffectively releasably lock said main body to said core tube, and whensaid main body is moved in an uphole direction relative to said coretube, self release from said inside surface of said core tube.

Preferably said braking mechanism includes a braking surface formedabout said main body, said braking surface provided with progressivelyincreasing outer diameter in an uphole direction; and, bias means forbiasing said brake elements in said uphole direction along said brakingsurface.

Preferably said braking mechanism further includes retaining means forretaining said braking elements about said main body.

Preferably each of said braking elements is in the form of a ball.

Preferably said core orientation indicating means includes a faceorientator having one or more orientation elements for providing saidorientation reference and, a shroud into which said one or moreorientation elements retract as said core drill is advanced onto a saidfacing surface.

Preferably said orientation device includes a tubular extension coupledto said shroud and extending into and slidably retained by said mainbody, said extension provided with a latching surface wherein said firstlatching means is held in engagement with said core lifter case assemblyby abutment of said first latching means with said latching surface,whereby in use, as said core drill is advanced onto said facing surface,said shroud contacts said bottom and slides toward said main body movingsaid latching surface out of abutment with said first latching meansthereby disengaging said first latching means from said core lifter caseassembly whereby said orientation device can retract into said coretube.

Preferably said core orientation indicating means includes a shaftpassing through said tubular extension and housing into said shroud andhaving a downhole end at which said one or more orientation elements aresupported.

Preferably said orientation device further includes first bias means forbiasing said tubular extension in a downhole direction and said latchingsurface into abutment with said first latching means.

Preferably said orientation device further includes: detent means forreleasably axially locking said shaft to said tubular extension; and,second bias means acting between said shaft and said tubular extensionfor biasing said shaft to move axially in an uphole direction relativeto said tubular extension when said detent means is released.

Preferably said detent means acts between said main body and saidtubular extension and is released as said core orientation indicatingmeans slides toward said main body prior to reaching said trigger point.

Preferably said shroud and said one or more orientation elements arerelatively dimensioned so that when said detent means is released saidshaft moves axially in an uphole direction by a distance sufficient sothat said orientation elements are wholly located within said shroud.

Preferably said core orientation indicating means includes a bottomorientator having a plurality of orientation balls and a plurality ofraces about which individual orientation balls can run, each race formedby two opposing race surfaces which are adapted to move relative to eachother between a free run position where said race surfaces are spacedsufficiently apart to allow an orientation ball therebetween to runfreely, and a clamp position wherein two adjacent race surfaces clamp anorientation ball therebetween to prevent said orientation ball from freerunning about said race.

Preferably said race surfaces are moved between said free run positionand said clamp position by said second bias means upon release of saiddetent means.

Preferably one or more of said race surfaces are formed of a materialwhich is sufficiently soft so that when said race surfaces are in saidclamp position an orientation ball therebetween indents said racesurfaces.

Preferably said races include at least one annular disc slidably mountedon said shaft.

Preferably said bottom orientation includes three orientation balls andsaid races include two annular discs slidably mounted on said shaft andrespective uphole and downhole end race surfaces supported on said shaftbetween which said annular discs are located, wherein said downhole endrace surface is fixed to a downhole side of said shaft and said upholeend race surface is slidably mounted on said shaft.

Preferably said orientation device further includes an inclinometerdisposed within said main body for providing an indication ofinclination of said orientation device when said core orientationindicating means is in contact with said facing surface.

Preferably said inclinometer is in the form of a rotatable wheel and,said shaft is moved toward said wheel to prevent rotation thereof whensaid detent means is released.

Preferably said wheel is mounted to rotate about first and secondmutually perpendicular axes.

Preferably said wheel is provided with a pair of ball bearings onopposite sides of an axis of said wheel and said inclinometer furtherincludes a circular race within which said ball bearings can run, saidcircular race having an axis coincident with a longitudinal axis of saidmain body.

In an alternate embodiment said shaft is rotatably held within saidtubular extension whereby said shaft can rotate about its longitudinalaxis relative to said shroud.

In this embodiment said orientation device includes a deadweightdisposed in said main body and coupled to said shaft to rotate saidshaft about its longitudinal axis by action of gravity to provide abottom of hole reference. As bottom orientation is achieved by thecombination of rotatably mounting the shaft and the provision of thedeadweight, this embodiment provides an alternate to the use of the balland race type bottom orientation.

According to a further aspect of the present invention there is provideda brake system for a tool travelling within a tubular element having aninner circumferential surface, said brake system including:

-   -   a plurality of brake elements;    -   a braking surface formed on said tool, said braking surface        having an outer diameter which progressively increases in a        first direction; and, first bias means for urging said brake        elements in said first direction, said braking surface and said        brake elements relatively dimensioned so that said brake        elements can be wedged between said braking surface and said        inner circumferential surface to lock said tool to said tubular        element in response to a force applied to said tool in a second        direction opposite to said first direction, and to brake or        retort the motion of said tool within said tubular element in        response to a force applied against the tool in said first        direction.

Preferably said brake system further includes an automaticallyreleasable brake lock having a first position where said lock holds saidbrake elements on a portion of said braking surface against the bias ofsaid first bias means where said brake elements cannot engage said innercircumferential surface, and a second position releasing said brakeelements to move under the influence of said first bias means along saidbraking surface in said first direction.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way ofexample only with reference to the accompanying drawings in which:

FIG. 1 is a section view of an embodiment of the orientation device;

FIG. 2 is a partial cutaway perspective view of the orientation deviceshown in FIG. 1;

FIG. 3 is a section view of the orientation device shown within a drillpipe at a first stage of operation;

FIG. 4 is a section view of the orientation device shown within a drillpipe at a second stage of operation;

FIG. 5 is a section view of the orientation device shown within a drillpipe at a third stage of operation;

FIG. 6 is an enlarged view of one end of the orientation device;

FIG. 7 is a section view of a second embodiment of the orientationdevice;

FIG. 8 is a partial cutaway perspective view of the orientation deviceshown in FIG. 7

FIG. 9 is a section view of a modified form of brake system incorporatedin the orientation device but applied to a running tool, with the brakesystem in a release position; and,

FIG. 10 is a section view of the brake system depicted in FIG. 9 in anapplied state.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1-6 of the accompanying drawings, an embodiment ofthe orientation device 10 in accordance with the present inventionincludes a main body 12 provided with a latching system 14 whichincludes first latches 16 and second latches 18. (As described ingreater detail hereinafter, the second latches 18 are in the form of abraking system). The latching system 14 operates to releasably latch thedevice 10 to a core lifter case assembly 20 (see FIG. 3) whichincorporates a core lifter coupled to a core tube 22 of a core drill 24used for cutting a core sample of the ground. The core lifter caseassembly 20, core tube 22, and core drill 24 are of conventionalconstruction and do not of themselves form part of the presentinvention.

A core orientation indicating means (hereinafter referred to as “coreorientator”) 26 is slidably coupled to the main body 12. The coreorientator 26 provides an orientation reference for the core sample cutby the core drill 24 by action of the core orientator 26 contacting thetoe (i.e. bottom facing surface) of the hole being drilled prior to thecommencement of drilling, i.e. the rotation of the core drill 24. Thecore orientator 26 is associated with the latching system 14 so thatupon sliding of the core orientator relative to the main body 12 beyonda trigger point, the core orientation 26 disengages the latching system14 from the core lifter case assembly 20 so that the orientation device10 is retracted into the core tube 22 by an advancing core which is cutafter commencement of drilling.

The orientation device 26 includes two main components, a VAN RUTH styleface orientator 28 which provides a plurality of reference pointsconforming with an end face of the core sample being cut and, a bottomorientator 30 which provides a reference line corresponding to thebottom of the hole cut by the core drill 24.

The face orientator 28 includes a plurality of circumferentiallyarranged orientation elements in the form of pins 32 which are retainedand can slide in respective holes 36 formed in a core block 34. Each ofthe pins 32 is formed with an enlarged head 38 which is dimensioned sothat it can not pass out from a lower end of a corresponding hole 36.The core block 34 is further provided with a circumferential cut-out 40inboard of a downhole end 42 of a core block 34. A plurality of rubberO-rings 44 is seated in the cut-out 40 about the pins 32 and act as abrake holding the pins 32 in position in the absence of a force appliedalong the length of the pins 32. The core block 34 is further providedwith an axial hole 46 which opens on to the downhole end 42. The hole 46accommodates a screw 48 which couples the core block 34 to a shaft 50 ofthe device 10. Retained between a head 50 of the screw 48 and the toe ofthe hole 46 is a core block spring 52 which acts to bias the core block34 toward the shaft 50. However, by virtue of this coupling, the coreblock 34 can be pulled against the bias of spring 52 to space it fromthe shaft 50. A locating pin 54 extends partially into holes 56 and 58formed in the core block 34 and shaft 50 respectively to fix therotational position of the core block 34 to the shaft 50.

The bottom orientator 30 includes a plurality (in this instance 3) balls60 a, 60 b and 60 c (hereinafter referred to in general as “balls 60”)disposed within respective races 62 a, 62 b, and 62 c respectively(hereinafter referred to in general as “races 62”). The races 62comprise two annular discs 64 a and 64 b which are slidably mounted onthe shaft 50, a cap 66 also slidably mounted on the shaft 50 on anuphole side of the discs 64, and an end stop 68 fixed to the shaft 50 ona downhole side of the discs 64. Race 62 a is defined between a racesurface 70 a formed on the end stop 68 and adjacent face 70 b of disc 64a. Race 62 b is defined between a race surface 70 b on an opposite sideof the disc 62 a, and facing race surface 70 c on disc 62 b; while therace 62 c is defined between race surface 70 e on an opposite side ofthe disc 64 b and a facing race surface 70 f on the cap 66. Bias meanssuch as annular spacing rubbers 73 are disposed between the mutuallyfacing race surfaces 70. (However, it is to be understood that therubbers can be replaced with other bias means such as springs.)

O-ring seals 72 and 74 are located in corresponding circumferentialgrooves formed on an outer circumferential surface of the end stop 68and cap 66 respectively. The cap 66 is also provided with a groove 76formed about its inner circumferential surface for seating an O-ring 78which bears against the outer surface of the shaft 50. A bush 80 isfixed to the shaft 50 on a side of the cap 66 opposite the end stop 68by a bush pin 82. The races 62 and in particular, annular discs 64 andspacing rubbers 72, 73 are enclosed by a sleeve 84.

Due to the construction of the bottom orientator 30, it will beappreciated that the width of the races 62 and thus the distance betweenopposing race surfaces 70 can be changed. More particularly, the racesurfaces can be moved between a free run position where the surfaces 70are spaced sufficiently apart to allow the balls 60 disposedtherebetween to freely run within the race 62 (as shown in FIGS. 1 and3) and a clamp position where the ball 60 disposed between a pair ofopposing race surfaces 70 is clamped by the surfaces thereby preventingit from rolling about the corresponding race 62 (shown in FIGS. 4 and5).

The orientation device 26 further includes a shroud 86 within which theface orientator 28 and bottom orientator 30 are disposed, and canretract into when the core drill 24 is lowered onto the bottom of ahole.

The shroud 86 is slidably retained by the body 12 via a locking housing88 to which the shroud 86 is threadingly coupled. The locking housing 88includes a generally tubular extension 90 which extends into the mainbody 12. The extension 90 is provided with an axial hole 92 throughwhich the shaft 50 extends. A recess 94 is formed on a side of thelocking housing 88 enclosed by the shroud 86 for seating the bush 80. Anouter surface of the extension 90 includes a first portion 96 at adownhole end of constant diameter followed by a contiguous andrelatively short portion 98 of lineally increasing outer diameterleading to a further portion 100 of constant diameter which terminatesin a radially outward step 102 followed by a short portion 104 ofconstant diameter then a radially inward step 106 leading to a finalportion 108 of constant diameter. A plurality of holes 110 is formed inthe portion 108 near, but inboard of a free end of the portion 108. Theholes 110 seat respective trigger balls 112. The combination of theportion 100 and step 102 on the outer surface of the extension 90 form alatch seat 114 for the latches 16. A circumferential groove 116 isformed in the locking housing 88 for seating an O-ring 118 that bearsagainst the outer surface of the shaft 50 passing through the hole 92.

An end of the shaft 50 which is disposed within the hole 92 is formedwith a blind axial hole 120 in which is disposed an inclinometer lockspring 122. The spring 122 is held within the hole 120 by a inclinometerlock pin 124 that partially extends into the hole 120 and partiallyextends from the free end of the shaft 50. The inclinometer lock pin 124is formed with an elongated hole or slot 126 through which a triggerseat pin 128 passes coupling the inclinometer lock pin 124 to the shaft50. The trigger lock pin 128 further extends on opposite sides into atrigger ball seat 130 which is disposed over the free end of the shaft50 and through which the inclinometer lock pin 124 extends.

A shaft spring 132 is disposed about the shaft 50 within the hole 92 andbears against the trigger ball seat 130. The spring 132 acts to bias theshaft 50 to move it in an uphole direction relative to the lockinghousing 88.

A locking spring 134 is located between the body 12 and portion 108 ofthe extension 90. The spring 134 bears at one end against the step 106and at an opposite end against a radial surface 136 formed internally ofthe body 12. The spring 134 biases the locking housing 88 in a downholedirection relative to the body 12.

The latches 16 are pivotally mounted on pivot pins 138 to the main body12 and extend through windows 140 formed in the body 12 (see FIG. 2).

The latch or brake system 18 includes a plurality of anchor balls 142which are retained by a anchor ball sleeve 144 disposed about a tailsection 146 of the main body 12. In this regard, the sleeve 144 isprovided with a plurality of holes 148 of a diameter less than thediameter of the balls 142 through which the balls 142 can protrude butnot fall out. The braking system further includes a braking surface 150formed about the tail section 146. The braking surface 150 is formedwith a gradually increasing outer diameter in a uphole direction, i.e. adirection away from the locking housing 88. A further surface 152 isformed about the tail section 146 adjacent the braking surface 50 but ofa smaller outer diameter. The two surfaces 150 and 152 are joined by ashort tapered surface 154. An anchor ball spring 156 is disposed aboutthe tail section of the body 12 and has one end seated against ashoulder 158 formed in the body 12 and an opposite end disposedwithin-he sleeve 144 and bearing against the anchor balls 142. Thespring 156 acts to bias the anchor balls 142 along the braking surface150 in the uphole direction.

The anchor balls 142 and braking surface 150 are dimensioned so that theballs 142 can ride along the braking surface 150 to wedge against aninner surface of the core tube 22 to produce a braking effect. Moreparticularly, when the device 10 is travelling in a downhole directionwithin the core drill 24 the trigger balls 142 lock the device 10 to thecore tube 22 preventing it from moving in the downhole direction and inparticular falling out of the end of the core drill 24. Further, byappropriate selection of the spring 156, the braking system 18 alsoprovides a braking effect against motion of the tool in an oppositedirection. The degree of braking effect is dependent on the springconstant of the spring 156. This braking effect is particularly usefulwhen the device 10, or another tool to which a similar braking system isapplied is used in an uphole configuration to reduce the speed of thedevice 10 or other tool when travelling back under the influence ofgravity.

An inclinometer 160 provided in the tail section 146 of the body 12. Theinclinometer 160 is in the form of a wheel 162 which is rotatablymounted about two mutually perpendicular axes 164 and 166. The wheel 162provided on its outer circumferential surface with a scale 168 providingan indication of the degree of inclination of the device 10 relative toa horizontal plane. The wheel 162 is weighted so that when it lies in ahorizontal plane, a 0° marking lies in the horizontal plane. The wheel162 is mounted within a circular bearing race 170 formed internally ofthe tail section 146. Ball bearings 172 are coupled to the wheel 162 atopposite ends of the axis of the wheel 162 which coincides with the axis164. In view of this mounting arrangement, it will be appreciated thatthe wheel 162 can rotate about the axis 164 and also rotate about theaxis 166.

The inside surface of the body 12, in the tail section 146 is formedwith a surface 174 of constant diameter against which the trigger balls112 can bear. The surface 174 leads in an uphole direction to anincreased inner diameter portion 176. The combination of the triggerballs 112, surface 174 and trigger ball seat 130 form a detent 133 (seeFIG. 6).

The operation of the device 10 will now be described in detail withparticular reference to FIGS. 3-5.

The device 10 is initially manipulated so that the pins 32 are pulled totheir maximum extent from the core block 34, the shroud 86 and lockinghousing pulled to their maximum extent from the body 12 and the shaft 50pulled to its maximum extent from the shroud 86. In this configuration,the latches 16 are seated on the latch seats 114 and abut the step 102and, the trigger balls 122 are held between the surface 174 and triggerball seat 130. Thus the spring 132 is held in relative compression andthe races 62 are in their free run position allowing the balls 60 tomove about the respective races 62 under the influence of gravity.

The device 10 is then inserted into the core tube 22 from the endprovided with the core lifter case assembly 20 with the tail section 146first. This insertion is halted when the latches 16 engage the end ofthe core lifter case assembly 20 as depicted in FIG. 3. With the coredrill 24 held in vertical or sub-vertical orientation, the device 10 isprevented from falling out of the core tube 22 (and thus core drill 24)by action of the braking system 18. In particular, the anchor balls 142are effectively wedged between the inside surface of the core tube 22and the braking surface 150 by the combined action of the spring 156 andthe weight of the device 10.

The core tube 22 is then lowered into a core drill 24 in a conventionalmanner. Initially, the drill 24 is held above the toe of the hole asufficient distance so that when the core tube 22 is properly locatedand seated within the core drill 24, the pins 32 are spaced from the toeof the hole. A drill operator then lowers the drill 24 onto the toe ofthe hole. It will be appreciated that as the races 62 are in their freerun position, the balls 60 will roll by action of gravity to a locationwhere they lie lowermost within the races.

As the drill is lowered on to the toe of the hole, the pins 32 contactthe face or surface of the hole. This surface constitutes the uppersurface of a core sample to be drilled with the core drill 24. The pins32 slide into the holes 36 of the core block 34 against resistance ofthe O-rings 44 providing profile reference points conforming to theconfiguration of the face of the core sample. The pins 32 maintain theirrelative position by virtue of the frictional forces applied by theO-rings 44.

As the core drill 24 is progressively lowered into the hole, a front endof the shroud 86 eventually contacts the toe of the hole. Accordingly,the weight of the core drill 24 is now loaded onto the shroud 86. Thiscauses the shroud 86 to move axially toward the body 12 with theextension 90 sliding into the body 12. This relative motion results inthe latch seat 114 being progressively slid away from the latches 16,and the trigger balls 112 being rolled along the surface 174 andeventually into the increased diameter section 176, as depicted in FIG.4.

When the trigger balls 112 reach the section 176 they are able to moveradially outwardly moving out of the trigger ball seat 130. Inconsequence, the spring 132 forces the shaft 50 to slide axially intothe body 12. This in turn forces the cap 66 against the locking housing88 compressing the spacing rubbers 73 and squeezing the races 62together to their clamp position where the orientation balls 60 areclamped against adjacent race surfaces 70. (The screw 48 and spring 52allows the shaft 50 to retract further into the extension 90 by actionof the spring 132 to place the race surfaces 70 in the clamp position).Accordingly, the position of the balls 60 when clamped provides anindication of the location of the lowest part of the hole from which acore sample being drilled by the core drill 24 is derived. Assumingperfect operation each of the three balls 60 will lie along a commonstraight line. However by providing three balls 60 a hithertounattainable degree of confidence in alignment accuracy assurance isprovided. If one of the races 62/balls 60 does not function correctlythe remaining two balls will lie on a line indicative of the bottom ofthe hole. If all three balls are out of alignment then an operator canbe very confident that the bottom of the hole orientation is unreliableand should be disregarded. In prior art one ball systems an operator isnever completely sure that a bottom hole orientation indicated isaccurate. Further, at this time, the inclinometer lock pin 124 advancetoward and contact the wheel 162 preventing it from further rotation byouter axis 164 to provide an indication of the inclination of the device10 at a point shortly prior to the commencement of cutting of the core.

Referring now to FIG. 5, it will be seen that as the core drill 24 isfurther lowered towards the toe of the hole, the extension 90 is pushedfurther into the body 12 against the bias of spring 134 to a positionwhere the latching seat 114 is moved from underneath the latches 16allowing them to rotate radially inwardly about respective pins 138.This radially inward movement is further facilitated by provision ofcomplimentary tapered surfaces on the latches 16 and the lifter case 20.

With the latches 16 now disengaged from the core lifter case assembly20, the further lowering of the core drill 24 into the bottom of thehole results in the entirety of the orientation device 10 sliding in anuphole direction within the core tube 22. The brake 18 does not preventsuch motion as the anchor balls 142 are able to be simply rolled alongthe braking surface 150/or surfaces 154 and 152 to a position where theydo not wedge against the inside surface of the core tube 22. This isfurther facilitated by virtue of the spring 156 not being able to resistthe weight of the core drill 24.

Just prior to the core drill 24 touching the toe of the hole, a drilloperator commences operation of the drill 24 causing it to rotate aboutits longitudinal axis. The core drill 24 can now cut a core sample ofthe ground. As the core sample is cut, it advances into the core drill24 entering the core lifter case assembly 20 and core tube 22. Thispushes the orientation device 10 further in the uphole direction withinthe core tube 22.

Once a length of core has been cut, the core drill 24 is stopped andlifted from the bottom of the hole. In this action, in the event thatthe core has not previously broken away from the ground from which it iscut, the core lifter case assembly 20 acts in a conventional mannergripping the core so that a tensile force can be applied to the core asthe drill 24 is lifted from the ground thereby braking the core sample.The core tube 22 can then be retrieved in a conventional manner leavingthe drill 24 in situ in the hole. The device 10 is retrieved with thecore tube 22. The device 10 can then be removed from the core tube 22together with the core sample. Since the face orientator 28 is disposedwithin the shroud 86, the configuration of the pins 32 is maintained andcan then be matched against the face of the core sample. Further, theorientation balls 60 are clamped by action of the spring 132 providingindication of the position of the bottom of the hole. This then allowsthe orientation of the core sample to be uniquely defined. Further, theinclinometer 60 provides an indication of the inclination of the coresample cut from the ground. Particularly, the inclinometer reading maybe taken by unscrewing a cap 165 inserting a sighting lens to the tailsection 146 to view the scale 168.

From the above description it will be appreciated that embodiments ofthe present invention are able to overcome the aforementioneddeficiencies in the prior art because the orientation of the core iseffectively “marked” prior to commencement of drilling and thus there isno need for a positive core break to retain the core orientationinformation, or to trip a separate tool to obtain the hole inclination.The device 10 is simply tripped with the core tube 22 rather thanrequiring separate tripping.

The core block 34 can be removed by unscrewing the screw 48 so as to beheld as a permanent record of core orientation with the core sample. Tothis end the outside of the core block or the core sample itself shouldbe marked with a line in alignment with the balls 60. Further, in suchan instance it is preferable if the core block 34 is made of arelatively cheap material such as plastics material.

A further embodiment of the core orientation device is depicted in FIGS.7 and 8 in which features the same, similar or perform equivalentfunctions as in the embodiment depicted in FIGS. 1-6 are denoted by thesame reference numbers but with the inclusion of a superscripted prime(′) symbol. The core orientator 10′ and core tube 22′ are depictedwithin a core drill 24′ includes at a downhole end a reamer 113 and coredrill bit 115. A stabilising ring 117 is also depicted coupled betweenthe drive within the core drill 24′. The core drill 24′, reamer 113,drill bit 115 and stabilising ring 117 are of conventional constructionand do not form part of the embodiment of the orientator 10′.

The main differences between the orientators 10 and 10′ are summarisedas follows. The body 12′ has a forward section 143 housing the lockingspring 134′ and provided with windows 140′ all of which are ofsubstantially similar configuration to the corresponding portion of thebody 12 of the first embodiment. The body portion 12′ also includes atail section 146′ provided with the surfaces 174′ and 176′ which,together with the trigger balls 112′ and trigger ball seat 130′ formdetent 133′. However, the forward section 143′ and tail section 146′ ofthe body 12′ are spaced by an integral tubular section 145.

The tail section 146′ houses a deadweight 147 which is attached to theshaft 50′ by a coupling 149 and pin 151. The deadweight 147 and coupling149 are able to rotate about the longitudinal axis of the shaft 50′. Tothis end, the coupling 149 is mounted in a bearing 153 having an outerrace which is seated against an inner circumferential surface of thetail section 146′. The deadweight 147 is provided with a longitudinalslot 155 along which the shaft 50′ can axially slide.

Inclinometer wheel 162′ is attached via an axle 157 to the deadweight147 at an end distant the face orientator 28′. Since the deadweight 147can rotate about the longitudinal axis of the shaft 50′ within the tailsection 146′, the inclinometer wheel 162′ is in effect able to rotateabout two perpendicular axes in a like manner as the wheel 162, theseaxes being the longitudinal axis of the shaft 50′ and the axis of axle157.

The second latches 18′ in the orientator 10′ are mounted about theintermediate section 145 of the body 12′. The latches 18 are in the formof pawls 159 which are pivotally coupled by pins 161 to the body 12′.Each pawl 159 is provided with a groove 163 on a radially outer surfacefor seating a spring 165. The spring 165 biases the pawls 159 radiallyoutward about pins 161 to enable abutment against a stop ring 167coupled between the core lifter case 20′ and core tube 22′.

As mentioned above, the shaft 50′ is able to rotate about itslongitudinal axis in the orientator 10′. To assist in facilitating thisrotational motion, the shaft 50′ is supported by a linear bearing 169housed within the tubular extension 90′ of the locking housing 88′, anda bearing 171 also housed within the extension 90′ but spaced from thelinear bearing 169 and adjacent the trigger ball seat 130′.

One end of the shaft spring 132′ abuts the linear bearing 169. Anopposite end of the spring 132′ is seated within a cup-shaped member 173which is attached to the shaft 50′ adjacent the bearing 171. It will befurther noted that the shaft 50′ at an end opposite the face orientator28′ is formed with a bifurcation 175 through which the pin 151 extends.

When the device 10′ and corresponding end of the core drill 24′ lie in anon-vertical plane, the deadweight 147 will rotate about thelongitudinal axis of the shaft 50′ to a position where it possesses theleast potential energy. That is, the deadweight 147 will position itselfthat it lies lower most within the body 12′. Since the shaft 50′ isattached via the coupling 149 to the deadweight 147, shaft 50′ and faceorientator 28′ are rotated with the deadweight 147′. It will berecognised that this functionality is equivalent to that provided by thebottom orientator 30 of the first embodiment.

The operation of the rotator 10′ will now be described.

The device 10′ is manipulated so that the shaft 50′ is pulled to itsmaximum extent out of the shroud 86′ with the pins 32′ also pulled outto the maximum extent. In this configuration the trigger balls 112′ areheld between the trigger ball seat 130′ and the surface 174′ axiallylocking the shaft 50′ to the shroud 86′ and tubular extension 90′. Thedevice 10 is then inserted rearwardly into the core of the case assembly20. The pawls 159 are able to pivot inwardly about pins 161 against thebias of spring 165 past the stop ring 167. When in this position, thelatches 16′ engage the end of the core lifter case as depicted in FIG.7.

With the core drill 24′ already in the hole, the core lifter tube 22 isthen lowered through the core drill 24′ in a conventional manner. Thedrill 24′ is held above the toe of the hole at sufficient distance sothat when the core tube 20 is properly located within the drill 24′, theelements 28′ are spaced from the toe of the hole. An operator thenlowers the drill 24′ to the toe of the hole. During the travel of thedevice 10′ and core tube 22′ through the drill 24′, the counterweight147 will have rotated within the tail section 146′ to the lowest pointwithin the housing 12′ by action of gravity. This in turn will haverotated the shaft 50′ and face orientator 28′ to provide a bottomreference for the face orientator 28′ and subsequent core cut by thedrill 24′.

As the drill 24′ is lowered onto the facing surface of the toe of thehole, the pins 28′ contact the facing surface and are pushed inwardlyinto the bush 34′ to provide profile reference points conforming to theconfiguration of the face of a core sample to be cut. The pins 28′ aremaintained in their position by virtue of frictional force existingbetween the pins 28′ and the core block 34′.

As the drill 24′ advances towards the toe of the hole, eventually theforward axial face of the shroud 86′ contacts the facing surface of thehole. Now the weight of the drill 24′ is loaded onto the shroud 86′.This causes the shroud 86′ to move axially toward the body 12′ with theextension 90′ projecting further into the body 12′. As a result thetrigger balls 112′ eventually roll onto the increased diameter portion176′ of the tail section 146′ axially releasing the shaft 50′ from theextension 90′. This releases the spring 132′ which drives the shaft 50′further in an uphole direction into the body 12′ so as to eventuallycontact the inclinometer wheel 162′ preventing it from further rotationabout the axle 157 to thus provide an indication of the inclination ofthe device 10′ at a time commensurate with the commencement of cuttingof the core.

Eventually, the shroud 86′ is pushed to a position where the latchingsurfaces 114′ are slid away from beneath the latches 16′ allowing thelatches to collapse or pivot inwardly thereby becoming disengaged fromthe core lifter case assembly 20′. Further lowering of the drill 24′onto the bottom of the hole results in the entirety of the device 10′sliding in an uphole direction within the core tube 22′.

The drill 24′ is then operated in a conventional manner to cut a core.As the core is being cut, it enters the core tube 22′ pushing the device10′ further in the uphole direction.

Once a length of core has been cut, the drill 24′ is stopped and liftedfrom the bottom of the hole. In this action, in the event that the coreis not previously broken away from the ground, the lifter case assembly20′ grips the core and a tensile force applied by the lifting of thedrill 24′ breaks the core from the ground. The core tube 22′ is thenretrieved in a conventional manner leaving the drill 111 in situ. Thedevice 10′ is retrieved with the core tube 22′. The device 10′ is thenremoved from the core tube 22′ together with the core sample. As thedeadweight 147 always self-locates to the lowest position within thebody 12′, by aligning the face of the core with the pins 28′, theorientation of the core within the ground can be determined. Further,the inclination of the core sample can be determined by viewing theinclinometer wheel 162′.

Prior to cutting the next length, the device 10′ is simply reloaded intothe core tube 22′ and the resulting ensemble then lowered through thedrill 24′ in a conventional manner and the sequence recommenced.

The braking system 18 used in the device 10 can be used in otherapplications and in particular to prevent loss of running tools andother downhole equipment in the event of failure or accidental releasefrom an overshot and/or wireline. In addition, as previously mentioned,the braking system also assists in reducing the speed of a running toolwhen returning under the action of gravity within drill string or drillpipe in an uphole orientation. Moreover, as depicted in FIGS. 9 and 10,the braking system 18 can be incorporated into a head assembly 200 ofany form of running tool or downhole device to hold the tool or devicewithin a drill pipe 202. The head assembly 200 includes a conventionalspearpoint 204 which is adapted for coupling to a conventional overshot206 provided with overshot latch dogs 208. The interaction and operationof the spearpoint 204 and overshot 206 is well known to those skilled inthe art and not described in any detail herein.

The head assembly 200 includes a shaft 210 which is fixed to thespearpoint 204. The shaft 210 is provided along a portion of the lengthof its outer circumferential surface with a braking surface 212 which istapered so as to gradually increase in outer diameter in a directiontoward a mouth of a hole into which the drill pipe 202 is disposed.Braking surface 212 terminates in a downhole side in a radially outwardstep 214 leading to a constant diameter portion 216 of the shaft 210.

A further tapered surface 218 is provided on the shaft 210 and tapers inthe same direction to the locking surface 212 so as to increase in outerdiameter in an uphole direction. The tapered surface 218 leads to aconstant diameter portion 220 which engages with the spearpoint 204. Theshaft 210 is provided with an enlarged portion 222 between the surfaces212 and 218.

An anchor ball sleeve 224 is slidably retained about the shaft 210 overthe braking surface 212. The sleeve 224 is provided with a plurality ofslots 226 through which anchor balls 228 can extend. The anchor balls228 are located to ride along the braking surface 212, the slots 226formed of a width less than the diameter of the anchor balls 228. A bush230 is located about the surface portion 216 of the shaft 210 that actsas a seat for a spring 232. The spring 232 is further retained by adetente washer 234 which sits on a spearhead base 236 which is coupledvia a pivot pin 238 to the downhole end of the shaft 210. The spring 232biases the anchor balls 228 to ride along the braking surface 212 toextend from the slots 226 to wedge against inner circumferential surface240 of the drill pipe 202.

The braking system 18 also includes an automatically releasable brakelock 242 which acts to ordinarily hold the anchor balls 228 out ofcontact with the inner surface 240 to allow free running of anassociated tool within the drill pipe 202 when attached to a overshot206, but automatically deploys of the anchor bolts 228 to lock or brakethe tool within the drill pipe 202 when the overshot 208 is releasedfrom the spearpoint 204.

The automatically releasable brake lock 242 includes an overshotextension sleeve 244, a cap 246, spring 248, locking sleeve 250, balls252 and floating sleeve 256. The overshot extension sleeve 244 isthreadingly coupled at one end to the overshot 206. The cap 246 isthreadingly coupled to an opposite end of the extension sleeve 244. Thecap 246 further slidably engages the locking sleeve 250, with the spring248 being disposed about the spearpoint 204 between the end of theextension sleeve 244 coupled to the overshot 206 and the locking sleeve250. The locking sleeve 250 is dimensioned so that it can extend overthe balls 252. The balls 252 are retained about the surface 218 by thefloating sleeve 256 which is provided with apertures 258 through whichthe balls 252 can extend. A further spring 260 is located within thefloating sleeve 256 and acts between the spearpoint 204 and the balls252 urging the balls 252 to roll to an end of the surface 228 with thesmallest outer diameter.

The spearhead base 236 is provided with a planar end surface 262 fromwhich extends an outwardly tapered surface 264 extending at an angle of45° relative to the surface 262.

When the overshot latch dogs 208 are engaged with the spearpoint 204,the spring 248 urges the locking sleeve 250 over the balls 252preventing them extending radially outwardly from the apertures 258. Inaddition, the floating sleeve 256 is forced in a downhole directionbearing against the anchor ball sleeve 224 forcing the anchor balls 228against the step 214 and thus disposed about a portion of the surface212 with the smallest outer diameter allowing the balls 228 to be spacedfrom the surface 240. In this configuration, the tool to which thebraking system 18′ is attached is able to run freely in any directionwithin the drive pipe 202.

However, if the latch dogs 208 become detached from the spearpoint 204while within the drill pipe 202, the brake lock 242 is automaticallyreleased deploying of the anchor balls 228. This arises as follows. Withthe disengagement of the latch dogs 208, the extension sleeve 244 whichis attached to the overshot 206 holds the locking sleeve 250 as thespearpoint 204 and remainder of the assembly 200 starts to fall draggingthe locking sleeve 250 with it. Thus in effect the locking sleeve 250 ispulled away from the balls 252. The balls 252 are now free to moveradially outwardly as they roll along the surface 218 toward thespearpoint 204 by action of the spring 232. In this regard, the spring232 urges the anchor ball sleeve 242 and thus the floating sleeve 256toward the spearpoint 204. With the locking sleeve 250 retracted, thefloating sleeve 256 can then roll the balls along the surface 218against the bias of the spring 260. Simultaneously, the spring 232 urgesthe anchor balls 228 to roll along the braking surface 212 which, due toits increasing outer diameter results in the balls 228 extending fromthe holes 226 and into contact with the surface 240.

Assuming for the time being that the drill pipe 202 is disposed in adownhole (as distinct from an uphole) the weight of the tool to whichthe braking system 18′ is attached together with the action of thespring 232 will effectively wedge the anchor balls 228 between thesurfaces 212 and 240 to lock the tool to the drill pipe 202. Now, afresh overshot 208 can be lowered into the hole to engage the spearpoint204. As the overshot is now retrieved by a wireline, it pulls thespearpoint 204 and shaft 210 in an uphole direction causing it to sliderelative to the anchor ball sleeve 224. As this occurs, the balls 228are able to roll along the braking surface 212 toward the step 214thereby releasing the balls 228 from engagement with the surface 240.Simultaneously, the floating sleeve 256 and locking sleeve 250 arecaused to slide relative to the shaft 210 back to the configurationdepicted in FIG. 7 so that the balls 252 effectively lock the anchorballs 228 from engagement with the surface 250.

In the event of an uphole application, the spring 232 can be providedwith an appropriate spring constant so as to urge the balls 228 intoengagement with the surface 240 to provide a braking effect as distinctfrom wedging against the surface 240 to lock an associated tool into thedrill pipe 202. This difference in operation is due to the fact thatgravity now acts in a direction which tends to roll the balls 228 alongthe braking surface 212 toward the step 214 where the balls are out ofengagement with the surface 210.

This then provides a manner for controlling the rate of descent of atool in an uphole disposed drill pipe, which would otherwise free falland smash against the head of the drill pipe.

Now that embodiments of the present invention have been described indetail it will be apparent to those skilled in the relevant arts thatnumerous modifications and variations may be made without departing fromthe basic inventive concepts. For example, the face orientator 28,28′ isdepicted as a VAN RUTH style orientator. However this may be replaced byother marking systems including, for example, a pad of malleablematerial which can take an impression of the facing surface of the toeof the hole, or even simply a marker which can mark the core such as aChina graph pencil. Further, a combination of pins 32 and markers may beused extending from the same core block 34.

In addition, if desired, a core tube extension can be coupled betweenthe core tube 22,22′ and a conventional back end for the purposes ofreceiving the device 10,10′ during a core run. The extension is in theform of a tube of the same length as the device 10,10′ and may beprovided with an internal shoulder or stop to provide an abutmentsurface for a portion of the shroud 86 or housing 88 located at aposition so that when the abutment engages the shroud 86 or housing 88the entirety of the device 10′ is located within the core tubeextension. This ensures that the core tube 22 is left entirely forreceipt of the core being cut and also provides protection of the device10,10′ in the event of over drilling of the core. In this instance, thecore would abut against the face of the shroud 86 which is made ofthickened material. Further, due to the abutment of the shroud 86 and/orhousing 88 with the core extension tube, any load applied by overdrilling of the core would essentially be borne on the shroud 86/housing88 and core extension tube, rather than being transmitted to theremainder of the device 10,10′.

All such variations and modifications are deemed to be within the scopeof the present invention the nature of which is to be determined fromthe above description and the appended claims.

1. An orientation device for providing an indication of the orientationof a core sample of material relative to a body of material from whichthe core is cut, said orientation device including at least: a main bodyprovided with a latching system for releasably latching the orientationdevice to a core lifter case assembly coupled to a core tube of a coredrill used to cut said core sample; and, a core orientation indicatingmeans slidably coupled to said main body for providing an orientationreference for said core sample by action of contacting a facing surfaceof said material to be drilled by said core drill prior to commencementof drilling, said core orientation indicating means operativelyassociated with said latching system whereby upon sliding of said coreorientation indicating means toward said main body beyond a triggerpoint facilitated by advancing said core drill onto said facing surfacesaid core orientation indicating means disengages said latching systemfrom said core lifter case assembly so that said orientation device isretracted into said core tube by an advancing core when said drill isoperated to cut said core.
 2. The orientation device according to claim1 wherein, said latching system includes first latching means forengaging said core lifter case assembly to prevent said main body frommoving in an uphole direction prior to core orientation indicating meansreaching said trigger point.
 3. The orientation device according toclaim 2 wherein, said latching system includes second latching means forengaging said core tube to prevent motion of said main body in adownhole direction.
 4. The orientation device according to claim 3wherein, said latching means includes a brake mechanism supported bysaid main body and having a plurality of brake elements which, when saidmain body is moved in a downhole direction relative to said core tube,wedge between said main body and an inner surface of said core tube withincreasing force to brake said relative motion and effectivelyreleasably lock said main body to said core tube, and when said mainbody is moved in an uphole direction relative to said core tube, selfrelease from said inside surface of said core tube.
 5. The orientationdevice according to claim 4 wherein, said braking mechanism includes abraking surface formed about said main body, said braking surfaceprovided with progressively increasing outer diameter in an upholedirection; and, brake bias means for biasing said brake elements in saiduphole direction along said braking surface.
 6. The orientation deviceaccording to claim 5 wherein, said braking mechanism further includesretaining means for retaining said braking elements about said mainbody.
 7. The orientation device according to claim 4, wherein, each ofsaid braking elements is in the form of a ball.
 8. The orientationdevice according to claim 1, wherein, said core orientation indicatingmeans includes a face orientator having one or more orientation elementsfor providing said orientation reference and, a shroud into which saidone or more orientation elements retract as said core drill is advancedonto said facing surface.
 9. The orientation device according to claim 8further including a tubular extension coupled to said shroud andextending into and slidably retained by said main body, said tubularextension provided with a latching surface wherein said first latchingmeans is held in engagement with said core lifter case assembly byabutment of said first latching means with said latching surface,whereby in use, as said core drill is advanced onto said facing surface,said shroud contacts said facing surface and slides toward said mainbody moving said latching surface out of abutment with said firstlatching means thereby disengaging said first latching means from saidcore lifter case assembly whereby said orientation device can retractinto said core tube.
 10. The orientation device according to claim 9wherein, said core orientation indicating means includes a shaft passingthrough said tubular extension and housing into said shroud and having adownhole end at which said one or more orientation elements aresupported.
 11. The orientation device according to claim 10 wherein,said orientation device further includes first bias means for biasingsaid tubular extension in a downhole direction and said latching surfaceinto abutment with said first latching means.
 12. The orientation deviceaccording to claim 11 wherein, said orientation device further includes:detent means for releasably axially locking said shaft to said tubularextension; and, second bias means acting between said shaft and saidtubular extension for biasing said shaft to move axially in an upholedirection relative to said tubular extension when said detent means isreleased.
 13. The orientation device according to claim 12 wherein, saiddetent means acts between said main body and said tubular extension andis released as said core orientation indicating means slides toward saidmain body prior to reaching said trigger point.
 14. The orientationdevice according to claim 13 wherein, said shroud and said one or moreorientation elements are relatively dimensioned so that when said detentmeans is released said shaft moves axially in an uphole direction by adistance sufficient so that said orientation elements are wholly locatedwithin said shroud.
 15. The orientation device according to claim 1,wherein, said core orientation indicating means includes a bottomorientator having a plurality of orientation balls and a plurality ofraces about which individual orientation balls can run, each race formedby two opposing race surfaces which are adapted to move relative to eachother between a free run position where said race surfaces are spacedsufficiently apart to allow an orientation ball therebetween to runfreely, and a clamp position wherein two adjacent race surfaces clamp anorientation ball therebetween to prevent said orientation ball from freerunning about said race.
 16. The orientation device according to claim15 wherein, said race surfaces are moved between said free run positionand said clamp position by said second bias means upon release of saiddetent means.
 17. The orientation device according to claim 15, wherein,one or more of said race surfaces are formed of a material which issufficiently soft so that when said race surfaces are in said clampposition an orientation ball therebetween indents said race surfaces.18. The orientation device according to claim 15, wherein, said racesinclude at least one annular disc slidably mounted on said shaft. 19.The orientation device according to claim 15, wherein, said bottomorientator includes three orientation balls and said races include twoannular discs slidably mounted on said shaft and respective uphole anddownhole end race surfaces supported on said shaft between which saidannular discs are located, wherein said downhole end race surface isfixed to a downhole side of said shaft and said uphole end race surfaceis slidably mounted on said shaft.
 20. The orientation device accordingto claim 1, wherein, said orientation device further includes aninclinometer disposed within said main body for providing an indicationof inclination of said orientation device when said core orientationindicating means is in contact with said facing surface.
 21. Theorientation device according to claim 20 wherein, said inclinometer isin the form of a rotatable wheel and, said shaft is moved toward saidwheel to prevent rotation thereof when said detent means is released.22. The orientation device according to claim 21 wherein, said wheel ismounted to rotate about first and second mutually perpendicular axes.23. The orientation device according to claim 22 wherein, said wheel isprovided with a pair of ball bearings on opposite sides of an axis ofsaid wheel and said inclinometer further includes a circular race withinwhich said ball bearings can run, said circular race having an axiscoincident with a longitudinal axis of said main body.
 24. Theorientation device according to claim 10, wherein, said shaft isrotatably held within said tubular extension whereby said shaft canrotate about its longitudinal axis relative to said shroud.
 25. Theorientation device according to claim 24 including a deadweight disposedin said main body and coupled to said shaft to rotate said shaft aboutits longitudinal axis by action of gravity to provide a bottom of holereference.
 26. The orientation device according to claim 24, wherein,said orientation device further includes an inclinometer disposed withinsaid main body for providing an indication of inclination of saidorientation device when said core orientation indicating means is incontact with said facing surface.
 27. The orientation device accordingto claim 26 wherein, said inclinometer is in the form of a rotatablewheel and, said shaft is moved toward said wheel to prevent rotationthereof when said detent means is released.
 28. The orientation deviceaccording to claim 27 wherein, said wheel is mounted to rotate aboutfirst and second mutually perpendicular axis.
 29. The orientation deviceaccording to claim 24, wherein, said second latching means includes twoor more pawls pivotally coupled to said main body and biased intocontact with an inner surface of said core lifter case assembly.
 30. Abrake system for a tool traveling with a tubular element having an innercircumferential surface, said brake system including: a plurality ofbrake elements; a braking surface formed on said tool, said brakingsurface having an outer diameter which progressively increases in afirst direction; and, first bias means for urging said brake elements insaid first direction, said braking surface and said brake elementsrelatively dimensioned so that said brake elements can be wedged betweensaid braking surface and said inner circumferential surface to lock saidtool to said tubular element in response to a force applied to said toolin a second direction opposite to said first direction, and to brake orretort the motion of said tool within said tubular element in responseto a force applied against the tool in said first direction.
 31. Thebrake system according to claim 30 wherein, an automatically releasablebrake lock having a first position where said lock holds said brakeelements on a portion of said braking surface against the bias of saidfirst bias means where said brake elements cannot engage said innercircumferential surface, and a second position releasing said brakeelements to move under the influence of said first bias means along saidbraking surface in said first direction.